A chemical vapor deposition method refers to a process for forming a thin film having a desired constitution onto a substrate by the steps of: transport of the vapor of a reactant to the substrate surface; adsorption of the reactant on the surface; chemical reaction and diffusion on the surface to form a thin film on the surface; and desorption of by-products from the surface. The chemical vapor deposition method has advantages in that: a thin film can be formed at a relatively low temperature; the film composition can be controlled; and it is possible to selectively deposit a film on a specific surface of a substrate. In a selective deposition method, a thin film is deposited on a desired area by way of enhancing the surface reactivity of the desired area toward the reactant.
Semiconductor devices have recently become highly integrated and the concomitant decrease in the line width of an integrated circuit pattern requires the use of advanced micro-processing techniques. For example, holes of updated semiconductor devices have much smaller diameters and higher aspect ratios than before.
A contact or via structure of a semi-conductor device is generally formed by depositing a metal in contact or via holes generated in an insulating layer, e.g., silicon oxide(SiO.sub.2), to form conductive metal plugs which connect the semiconductor substrate or metal layer with a wiring layer. Such metal plugs are conventionally prepared by blanket deposition and etch-back which is explained in conjunction with FIGS. 1A and 1B, as follows:
First, an insulating layer(20), e.g., a silicon oxide(SiO.sub.2) layer is deposited on a silicon substrate(10) and a contact or via hole(30) is generated through the insulating layer(20) by a conventional etching method. Subsequently, a metal is vapor-deposited both on the top surface of the insulating layer(20) and the inside of the hole(30) to form a continuous metal layer(40). Then, the metal layer is etched back to obtain a metal plug(40) as shown in FIG. 1B. However, the step of forming the metal plug by etching the metal layer is cumbersome and requires complicated lithographic techniques.
In order to solve the above problem, selective metal deposition in holes has been attempted(see M. J. Hampden-Smith et al., Chem. Vap. Deposition, 1(2), 1995), as is explained below, in conjunction with FIGS. 2A and 2B.
An insulating layer(120) containing a hole (130) is formed on top of a silicon substrate(110) in a conventional manner, and then, a metal layer (140) is formed within the hole (130) by a surface-selective chemical vapor deposition method to form a filled hole as shown in FIG. 2A.
However, the above surface-selective thin layer formation process can not be applied in case when the hole and insulating layer are covered with a same surface, e.g., a diffusion barrier. Further, the surface-selectivity is easily lost.
Therefore, there has existed a need to develop a cost-effective, simple method to fabricate a contact or via structure of a semi-conductor devices.